Active vibration controller

Abstract

An active vibration controller includes acceleration detectors for generating output signals on the basis of vibrations of a vehicle, speakers provided in a vehicle's cabin, microphones provided in the vehicle's cabin for receiving generated sounds from the speakers and road noises generated on the basis of running of the vehicle, and adaptive digital filters using output signals from the acceleration detectors as inputs for controlling filter factors on the basis of an RLS algorithm to minimize levels of output signals from the microphones in response to output signals from the microphones and output signals from the acceleration detectors through use of a transfer function matched to the transfer function of the vehicle's cabin in a sound field between the speakers and the microphones. The controller minimized levels of output signals from the microphones by developing an applied output signal to the speakers. Thus parameters of the filter factors are adaptively updated in accordance with identified system characteristics, providing satisfactory estimation accuracy, and quick convergence to changed sensed noise to silence road noise in the vehicle's cabin.

What is claimed is: 
     
       1. An active vibration controller controlling vibration within a sound field comprising: a first vibration detector generating reference input signals in response to detected vibrations from vibration generating sources;   a controllable vibration source provided in the sound field;   a second vibration detector provided in the sound field for receiving vibrations generated in the sound field by said controllable vibration source and by vibrations generated in said sound field from said vibration generating sources, and generating an error signal on the basis of differences between both said vibrations; and   an adaptive digital filter, using the reference input signal and the error signal as inputs and having filter factors updated in real time in accordance with an updating parameter recursively updated and processed, with an initial value of the updating parameter being a predetermined positive real number, by using the reference input signals outputted from said first vibration detector, said adaptive digital filter minimizing the error signal by energizing said controllable vibration source to reduce vibrations in said sound field;   said digital filter calculating said filter factors using a recursive least squares algorithm having a forgetting factor.   
     
     
       2. The active vibration controller of claim 1 wherein said adaptive digital filter selects filter factors to increase the speed of convergence of the error signal. 
     
     
       3. The active vibration controller according to claim 1, wherein said adaptive digital filter includes a digital signal processor calculating and updating the filter factors. 
     
     
       4. The active vibration controller according to claim 1, wherein said updating parameter to be recursively updated is weighed. 
     
     
       5. The active vibration controller according to claim 1, wherein said controller uses plural first vibration detectors respectively provided at different positions on a vehicle, said first vibration detectors each being a noise detector. 
     
     
       6. The active vibration controller according to claim 5, wherein the vehicle includes a suspension and wherein said noise detectors detect noises generated in the suspension of the vehicle. 
     
     
       7. The active vibration controller according to claim 5, wherein the vehicle includes a body and wherein said noise detectors are noise detectors installed on the body of the vehicle for detecting noises generated in the body of the vehicle. 
     
     
       8. The active vibration controller according to claim 1, wherein said controllable vibration source includes a plurality of speakers respectively provided at different positions in a vehicle's cabin. 
     
     
       9. The active vibration controller according to claim 1, wherein said controller uses plural second vibration detectors respectively provided at different positions in a vehicle's cabin, said second vibration detectors are sound microphones. 
     
     
       10. The active vibration controller of claim 1 wherein the initial value is stored in a ROM. 
     
     
       11. An active vibration controller controlling vibration within a sound field comprising: a source vibration detector positioned in a vibration transmission path between an undesired vibration source and the sound field, said source vibration detector detecting undesired vibration and developing an undesired vibration signal representing the vibration produced by said undesired vibration source;   a sound field vibration sensor disposed within the sound field, monitoring vibrations within the sound field and developing a sound field vibration signal representative of the vibrations within the sound field;   a noise path transfer function filter, operatively connected to said source vibration detector, and electronically simulating the transfer characteristic of the transmission path between the source vibration detector and the sound field, said noise path transfer function filter filtering the undesired vibration signal to develop a vibration simulation signal estimating the vibration received by the sound field from said undesired vibration source;   a cancellation vibration source disposed to introduce cancellation vibrations within the sound field to cancel vibration in the sound field originating from the undesired vibration source;   an adaptive filter filtering the undesired vibration signal to produce a vibration cancellation signal supplied to said cancellation vibration source; and   means, responsive to the vibration simulation signal and the sound field vibration signal, for determining filter factors to be used by said adaptive filter to produce said vibration cancellation signal, said means for determining using a recursive least squares algorithm to determine the filter factors and recursively update the filter factors with an updating parameter, wherein the recursive least squares algorithm uses an initial value for the updating parameter which is a predetermined positive real number, and wherein said recursive least squares algorithm utilizes a forgetting factor for determining the filter factors.   
     
     
       12. The active vibration controller of claim 11 wherein said means for determining uses a multiple error filtered×Recursive Least Squares (Mef×-RLS) algorithm to determine the filter factors. 
     
     
       13. The active vibration controller of claim 12 wherein said means for determining uses the Mef×-RLS algorithm to update the filter factors in real time to minimize levels of an error signal used to produce said vibration cancellation signal. 
     
     
       14. The active vibration controller of claim 11 wherein said adaptive filter is a digital FIR (finite impulse response) filter. 
     
     
       15. The active vibration controller of claim 11 wherein said recursive least squares algorithm increases the rate of filter convergence of said adaptive filter in response to changes in the characteristics of the undesired vibration detected by said source vibration detector. 
     
     
       16. The active vibration controller of claim 11 wherein the forgetting factor has a constant value. 
     
     
       17. The active vibration controller of claim 11 wherein the forgetting factor is adaptively varied. 
     
     
       18. The active vibration controller of claim 11 wherein the forgetting factor is asymptotically approaches "1". 
     
     
       19. The active vibration controller of claim 11 wherein said adaptive filter is an adaptive digital filter with two taps. 
     
     
       20. The active vibration controller of claim 11 wherein said sound field is disposed within the cabin of a passenger vehicle. 
     
     
       21. The active vibration controller of claim 20 wherein said passenger vehicle is a wheeled passenger vehicle, said source vibration detector being suspension mounted and detecting noise generated in the vehicle's suspension. 
     
     
       22. The active vibration controller of claim 20 wherein said passenger vehicle is a wheeled passenger vehicle, said source vibration detector being installed on a vehicle's body for detecting noises generated in said vehicle's body. 
     
     
       23. The active vibration controller of claim 20 wherein said controller uses plural source vibration detectors respectively provided at different positions on the vehicle, said source vibration detectors each being a noise detector. 
     
     
       24. The active vibration controller of claim according to claim 11, wherein said cancellation vibration source includes plural speakers respectively provided at different positions in a vehicle's cabin. 
     
     
       25. The active vibration controller of claim 11 wherein the initial value is stored in a ROM. 
     
     
       26. A method of controlling vibration within a sound field comprising: detecting undesired vibration at a source noise detection location disposed along a vibration transmission path between an undesired vibration source and the sound field and producing an undesired vibration signal in response thereto;   monitoring vibrations within the sound field and producing a sound field vibration signal in response thereto;   electronically simulating the transfer characteristic of the transmission path between the source noise detection location and the sound field and modifying the undesired vibration signal therewith to develop a vibration simulation signal estimating the vibration received by the sound field from said undesired vibration source;   adaptively filtering the undesired vibration signal with an adaptive filter to produce a vibration cancellation signal;   converting said vibration cancellation signal into cancellation vibrations and supplying the cancellation vibrations to the sound field to cancel the undesired vibrations in the sound field originating from the undesired vibration source;   said step of filtering including determining filter factors to be used by said adaptive filter based on said vibration simulation signal and the sound field vibration signal to produce said vibration cancellation signal by using a recursive least squares algorithm to determine the filter factors and recursively update the filter factors with an updating parameter, wherein the recursive least squares algorithm uses an initial value for the updating parameter which is a predetermined positive real number, and wherein said step of determining filter factors uses the recursive least squares algorithm while utilizing a forgetting factor in the development of the filter factors.   
     
     
       27. The method of claim 26 wherein said step of determining uses a multiple error filtered×Recursive Least Squares (Mef×-RLS) algorithm to determine the filter factors. 
     
     
       28. The method of claim 27 wherein said step of determining uses the Mef×-RLS algorithm to update the filter factors in real time to minimize levels of an error signal used to produce said vibration cancellation signal. 
     
     
       29. The method of claim 26 wherein said step of adaptively filtering employs a digital FIR (finite impulse response) filter. 
     
     
       30. The method of claim 26 wherein said step of determining uses the recursive least squares algorithm to increase the rate of filter convergence of said step of adaptive filtering in response to changes in the characteristics of the undesired vibration. 
     
     
       31. The method of claim 26 wherein the forgetting factor has a constant value. 
     
     
       32. The method of claim 26 wherein said step of determining adaptively varies the forgetting factor. 
     
     
       33. The method of claim 26 wherein the forgetting factor asymptotically approaches "1". 
     
     
       34. The method of claim 26 wherein said sound field is disposed within the cabin of a passenger vehicle. 
     
     
       35. The method of controlling vibration according to claim 26 further including the step of storing the initial value in a ROM.